The present invention relates generally to wax compositions for construction board applications. More particularly the invention is concerned with, among other things, a method for determining the suitability of various waxes for use in construction board applications, and for preparing suitable wax compositions.
Composite board products used in construction applications such as particleboard, medium density fiberboard, oriented strand board and the like have been produced for many years and their method of manufacture is well known in the industry.
The primary component of these composite materials is a natural fibrous material. In forming the board product the fibrous material typically is combined with a minor amount of resin and a waxy composition, formed into sheets and subjected to pressure and heat.
In selecting wax compositions for use in construction board applications the focus has theretofore been placed on oil content and stream grade or viscosity range, i.e., the SUS viscosity at 100xc2x0 F. This viscosity typically is given as a xe2x80x9cNeutralxe2x80x9d member, e.g., 100N, 300N etc. In any event, previous studies, using both emulsions and neat applications of waxes have shown trends indicating improved board properties with lighter stream grade waxes, e.g., below grade 30 (550N) and for waxes with lower oil content. For example xe2x80x9cThe Effect of Wax Type and Content on Waferboard Propertiesxe2x80x9d, Hsu, et al, International Particleboard/Composite Materials Symposium, Apr. 3-5, 1990, pp. 85-93 discusses waferboard swelling in response to 0 to 45% wax content and 0 to 30 wt % oil content; and U.S. Pat. No. 6,183,849 discloses preparing composite boards using waxes with oil content greater than 30 wt %.
Experience has shown that use of low wax stream grades, i.e., grades below 30 (550N) in producing composite boards, board quality and performance typically is fine; however, when using high wax stream grade, i.e., above about 30 (550N) problems with board quality often are encountered. This is particularly troublesome since it often is desirable to employ higher grade stream waxes for safety and environmental reasons. For example, in the production of oriented strand boards heavy steam grade waxes are desirable to minimize volatility in presses that typically operate at over 400xc2x0 F. (205xc2x0 C.).
Consequently, there is a need to be able to predict the suitability of a wax composition for composite board manufacture, and to be able to adjust the wax composition, if needed, to be suitable for such board manufacture. Also, there is a need to be able to adjust the volatility of wax compositions to be used in construction board applications to meet emission requirements. Additionally, the ability to blend numerous product streams into a suitable wax composition offers suppliers flexibility in meeting market needs. The present invention is directed to these and other needs.
Very simply, the present invention is based on the discovery that the n-paraffin content of a wax composition is the key compositional parameter for waxes used in construction board and this n-paraffin content should be at least 21 wt % for the wax composition to be suitable. Thus the suitability of a wax for construction board applications can be determined based on its n-paraffin content, and blends of waxes and oils and oils can be composed to meet the required n-paraffin content.
These, and other features, will be described in greater detail hereinafter.